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1.  Age-related differences in enhancement and suppression of neural activity underlying selective attention in matched young and old adults 
Brain research  2013;1499:69-79.
Selective attention reflects the top-down control of sensory processing that is mediated by enhancement or inhibition of neural activity. ERPs were used to investigate age-related differences in neural activity in an experiment examining selective attention to color under Attend and Ignore conditions, as well as under a Neutral condition in which color was task-irrelevant. We sought to determine whether differences in neural activity between old and young adult subjects were due to differences in age rather than executive capacity. Old subjects were matched to two groups of young subjects on the basis of neuropsychological test performance: one using age-appropriate norms and the other using test scores not adjusted for age. We found that old and young subject groups did not differ in the overall modulation of selective attention between Attend and Ignore conditions, as indexed by the size of the anterior Selection Positivity. However, in contrast to either young adult group, old subjects did not exhibit reduced neural activity under the Ignore relative to Neutral condition, but showed enhanced activity under the Attend condition. The onset and peak of the Selection Positivity occurred later for old than young subjects. In summary, older adults execute selective attention less efficiently than matched younger subjects, with slowed processing and failed suppression under Ignore. Increased enhancement under Attend may serve as a compensatory mechanism.
doi:10.1016/j.brainres.2013.01.003
PMCID: PMC3570693  PMID: 23313874
Visual Selective Attention; Aging; ERPs; Executive capacity; Top-Down Processing; Inhibition; Well-matched Subjects
2.  Brain amyloid and cognition in Lewy body diseases 
Background
Many patients with Parkinson disease (PD) develop dementia (PDD), a syndrome that overlaps clinically and pathologically with dementia with Lewy bodies (DLB); PDD and DLB differ chiefly in the relative timing of dementia and parkinsonism. Brain amyloid deposition is an early feature of DLB and may account in part for its early dementia. We sought to confirm this hypothesis and also to determine whether amyloid accumulation contributes to cognitive impairment and dementia in the broad range of parkinsonian diseases.
Methods
29 cognitively normal PD, 14 PD subjects with mild cognitive impairment (PD-MCI), 18 with DLB, 12 with PDD and 85 healthy control subjects (HCS) underwent standardized neurologic and neuropsychological examinations and PiB imaging with PET. Apolipoprotein (APOE) genotypes were obtained in many patients. PiB retention was expressed as the distribution volume ratio using a cerebellar tissue reference.
Results
PiB retention was significantly higher in DLB than in any of the other diagnostic groups. PiB retention did not differ across PDD, PD-MCI, PD, and HCS. Amyloid burden increased with age and with the presence of the APOEε4 allele in all patient groups. Only in the DLB group was amyloid deposition associated with impaired cognition.
Conclusions
DLB subjects have higher amyloid burden than subjects with PDD, PD-MCI, PD or HCS; amyloid deposits are linked to cognitive impairment only in DLB. Early amyloid deposits in DLB relative to PDD may account for their difference in the timing of dementia and parkinsonism.
doi:10.1002/mds.25048
PMCID: PMC3725259  PMID: 22693110
dementia; Lewy; Parkinson; amyloid; PiB
3.  Amyloid-β Associated Cortical Thinning in Clinically Normal Elderly 
Annals of neurology  2011;69(6):1032-1042.
Introduction
Both amyloid-β (Aβ) deposition and brain atrophy are invariably associated with Alzheimer's disease (AD) and the disease process likely begins many years before symptoms appear.
Objective
We sought to determine whether clinically normal (CN) older individuals with Aβ deposition revealed by PET imaging using Pittsburgh Compound B (PiB) also have evidence of both cortical thickness and hippocampal volume reductions in a pattern similar to that seen in AD.
Methods
One hundred and nineteen older individuals (87 CN subjects and 32 patients with mild AD) underwent PiB PET and high-resolution structural MR. Regression models were used to relate PiB retention to cortical thickness and hippocampal volume.
Results
We found that PiB retention in CN subjects was (1) age-related and (2) associated with cortical thickness reductions particularly in parietal and posterior cingulate regions extending into the precuneus, in a pattern similar to that observed in mild AD. Hippocampal volume reduction was variably related to Aβ deposition.
Interpretation
We conclude that Aβ deposition is associated with a pattern of cortical thickness reduction consistent with AD prior to the development of cognitive impairment.
doi:10.1002/ana.22333
PMCID: PMC3117980  PMID: 21437929
4.  Imaging amyloid deposition in Lewy body diseases 
Neurology  2008;71(12):903-910.
Background:
Extrapyramidal motor symptoms precede dementia in Parkinson disease (PDD) by many years, whereas dementia occurs early in dementia with Lewy bodies (DLB). Despite this clinical distinction, the neuropsychological and neuropathologic features of these conditions overlap. In addition to widespread distribution of Lewy bodies, both diseases have variable burdens of neuritic plaques and neurofibrillary tangles characteristic of Alzheimer disease (AD).
Objectives:
To determine whether amyloid deposition, as assessed by PET imaging with the β-amyloid–binding compound Pittsburgh Compound B (PiB), can distinguish DLB from PDD, and to assess whether regional patterns of amyloid deposition correlate with specific motor or cognitive features.
Methods:
Eight DLB, 7 PDD, 11 Parkinson disease (PD), 15 AD, and 37 normal control (NC) subjects underwent PiB-PET imaging and neuropsychological assessment. Amyloid burden was quantified using the PiB distribution volume ratio.
Results:
Cortical amyloid burden was higher in the DLB group than in the PDD group, comparable to the AD group. Amyloid deposition in the PDD group was low, comparable to the PD and NC groups. Relative to global cortical retention, occipital PiB retention was lower in the AD group than in the other groups. For the DLB, PDD, and PD groups, amyloid deposition in the parietal (lateral and precuneus)/posterior cingulate region was related to visuospatial impairment. Striatal PiB retention in the DLB and PDD groups was associated with less impaired motor function.
Conclusions:
Global cortical amyloid burden is high in dementia with Lewy bodies (DLB) but low in Parkinson disease dementia. These data suggest that β-amyloid may contribute selectively to the cognitive impairment of DLB and may contribute to the timing of dementia relative to the motor signs of parkinsonism.
GLOSSARY
= Automated Anatomic Labeling;
= Alzheimer disease;
= Alzheimer’s Disease Research Center;
= American version of the National Adult Reading Test;
= analysis of covariance;
= Blessed Dementia Scale;
= cerebral amyloid angiopathy;
= Clinical Dementia Rating;
= Clinical Dementia Rating Sum of Boxes;
= dementia with Lewy bodies;
= distribution volume ratio;
= Cued Selective Reminding Test;
= Free Selective Reminding Test;
= Hoehn and Yahr;
= Massachusetts General Hospital;
= Mini-Mental State Examination;
= normal control;
= neurofibrillary tangle;
= Neuropsychiatric Inventory Questionnaire;
= not significant;
= Parkinson disease;
= Parkinson disease dementia;
= Pittsburgh Compound B;
= region of interest;
= Statistical Parametric Mapping;
= UK Parkinson’s Disease Society Brain Bank Research Center;
= United Parkinson’s Disease Rating Scale;
= Wechsler Adult Intelligence Scale–Revised.
doi:10.1212/01.wnl.0000326146.60732.d6
PMCID: PMC2637553  PMID: 18794492
5.  Imaging amyloid deposition in Lewy body diseases 
Neurology  2008;71(12):903-910.
Background
Extrapyramidal motor symptoms precede dementia in Parkinson disease (PDD) by many years, whereas dementia occurs early in dementia with Lewy bodies (DLB). Despite this clinical distinction, the neuropsychological and neuropathologic features of these conditions overlap. In addition to widespread distribution of Lewy bodies, both diseases have variable burdens of neuritic plaques and neurofibrillary tangles characteristic of Alzheimer disease (AD).
Objectives
To determine whether amyloid deposition, as assessed by PET imaging with the β-amyloid–binding compound Pittsburgh Compound B (PiB), can distinguish DLB from PDD, and to assess whether regional patterns of amyloid deposition correlate with specific motor or cognitive features.
Methods
Eight DLB, 7 PDD, 11 Parkinson disease (PD), 15 AD, and 37 normal control (NC) subjects underwent PiB-PET imaging and neuropsychological assessment. Amyloid burden was quantified using the PiB distribution volume ratio.
Results
Cortical amyloid burden was higher in the DLB group than in the PDD group, comparable to the AD group. Amyloid deposition in the PDD group was low, comparable to the PD and NC groups. Relative to global cortical retention, occipital PiB retention was lower in the AD group than in the other groups. For the DLB, PDD, and PD groups, amyloid deposition in the parietal (lateral and precuneus)/posterior cingulate region was related to visuospatial impairment. Striatal PiB retention in the DLB and PDD groups was associated with less impaired motor function.
Conclusions
Global cortical amyloid burden is high in dementia with Lewy bodies (DLB) but low in Parkinson disease dementia. These data suggest that β-amyloid may contribute selectively to the cognitive impairment of DLB and may contribute to the timing of dementia relative to the motor signs of parkinsonism.
doi:10.1212/01.wnl.0000326146.60732.d6
PMCID: PMC2637553  PMID: 18794492

Results 1-5 (5)